LOS ALAMOS, N.M. (AP) - The threat of wildfire reaching the Los Alamos nuclear lab and the town that surrounds it eased after crews made progress under cloud cover and rain, but concerns turned Friday to lands held sacred by Native American tribes as firefighters braced for a hot, dry weekend.

The fire has blackened more than 162 square miles in the last six days, making it the largest fire in New Mexico history. Erratic winds and dry fuels helped it surpass the 2003 Dry Lakes fire, which took five months to burn through 94,000 acres in the Gila National Forest.

More than 1,200 firefighters were on the lines Friday trying to slow down the flames as National Guard troops, state police officers and local deputies patrolled neighborhoods and enforced evacuation orders.

“This is the biggest fire in the history of our state and it’s not over yet,” U.S. Sen. Jeff Bingaman, D-N.M., said during a briefing in the heart of Los Alamos. “We’re all very keenly aware of that.”

The Los Alamos National Laboratory remained closed, and fire officials said there was no chance the thousands of evacuated residents and lab employees would be able to resume their normal lives Friday.

Still, the fire chiefs in charge of battling the massive blaze were confident since their crews were keeping flames from spreading down a canyon that leads to the lab and the town.

The challenge Friday was stopping the flames from doing more damage to the lands of Santa Clara Pueblo. The fire had made a four-mile run north toward the reservation, hitting the pueblo’s watershed and cultural sites that are scattered on the Pajarito Plateau.

Fire operations section chief Jerome Macdonald said parts of the fire in Santa Clara canyon burned hot while others saw less damage because of overnight temperatures and lighter winds.

Conditions in the area are so dry that the fire has been burning downed trees that were scorched in the huge Cerro Grande fire in 2000. It also burned through moisture-rich aspen trees to push into the canyon.

“This is a fire like we’ve never seen before,” Santa Clara Pueblo Gov. Walter Dasheno told The Associated Press in a telephone interview.

He said his people are devastated by the news coming in from the front lines of the firefighting efforts _ cultural sites destroyed, forest resources lost and plants and animals that the pueblo’s 2,800 residents depend on gone.

“We cried when we saw Mother Nature doing what she was doing to our canyon area. We were helpless,” Dasheno said.

He said the tribe has discussed the possibility of evacuating if the fire grew closer. Community meetings were being held each day to keep residents informed.

Santa Clara is not the only Indian community to feel the effects of the fire. Much of the plateau _ which includes hundreds of archaeological sites at Bandelier National Monument _ holds great significance to the surrounding tribes.

In Los Alamos, crews continued to work Friday at the bottom of Los Alamos Canyon. Fire Chief Doug Tucker said the area that was burning previously was thinned, providing a safe area for firefighters to attack the flames.

Los Alamos Canyon runs past runs past the old Manhattan Project site in town and a 1940s-era dump site where workers are near the end of a cleanup project of low-level radioactive waste. The World War II Manhattan Project developed the first atomic bomb, and workers from the era dumped hazardous and radioactive waste in trenches along six acres atop the mesa where the town sits.

The canyon also runs through town and a portion of the northern end of the lab, where a weapons research nuclear reactor was located until it was demolished in 2003.

The fire burned upslope at least three miles from the sites and didn’t pose an immediate threat. Fire had crept to within a half-mile of homes in town.

“We feel quite confident. In fact, we feel extremely confident that the situation is well in hand with respect to protecting our facilities, protecting the equipment and the material that exists on this property,” said Tom D’Agostino, head of the National Nuclear Security Administration, which oversees the lab.

D’Agostino toured some of the burned area Friday. What was so striking, he said was the “grit and determination” of the people working to protect the area.

“We don’t let our guard down for one second because we know how vitally important it is to keep on top of this problem,” he said.

The lab has been closed since Monday, when the town of Los Alamos and some of its surrounding areas _ 12,000 people in all _ were evacuated. There was no word on when it would reopen or when residents would be allowed back home.

Officials said the lab has some 10,000 experiments running at the same time that have been put on hold. Those include studies on materials needed to extend the life of 1960s-era B61 nuclear bombs as well as experiments run on two supercomputers.

The lab works on such topics as renewable energy and particle physics, solar flares, forensics on terrorist attacks, and studying the AIDS virus at the molecular level to help scientists develop strategies for developing vaccines.

On Monday, about an acre of lab property burned, raising concerns about possible contamination from material stored or buried on lab grounds. As a precaution, the government sent a plane equipped with radiation monitors over the lab. Samples analyzed so far from some of the lab’s monitors show nothing abnormal in the smoke.

Lab authorities, along with outside experts on nuclear engineering, expressed confidence that the blaze would not scatter radioactive material, as some in surrounding communities feared.

Macdonald said there was hope that crews would be able to gain on the fire since it was close to two large burn scars left by previous fires.